1. Field of the Invention
This invention relates to a door lock/unlock system for a vehicle, and, more particularly, to a door lock/unlock system provided with an antitheft feature.
2. Description of Related Art
In recent years, vehicles are typically equipped with a door lock/unlock system having a power lock feature that a door lock/unlock mechanism is actuated by an electric actuator to lock and unlock a vehicle door. With such a door lock/unlock system, when manually locking or unlocking a door beside a driver's seat, other doors are correspondingly locked or unlocked by means of an electric actuator all at once. Even when the lock/unlock mechanism is in a lock state or in an unlock state, each of the doors is unlocked by manually operating a related interior door lock knob. Accordingly, it is possible for burglars or persons other than the owner of the vehicle to unlock a door in an unfair manner, for example by breaking a window glass and operating the interior door lock knob with a hand or by operating the interior door lock knob with a metal wire or a metal stick inserted through a gap between a window frame and a window glass. In order to prevent a vehicle from robbery or theft, there have been proposed restraint door lock system of the type equipped with a power lock mechanism and a restraint door lock mechanism which makes the door lock/unlock mechanism inoperative unless the door key inserted in the key cylinder is operated with intention of opening the door and even, for example, when the interior door lock knob is operated to unlock the door. Such a restraint door lock system is known from, for example, Japanese Patent Application laid-open to the public as Publication No. 2-171485.
It is noted that the term "super lock" as used hereafter in the specification refers to a state that the lock/unlock mechanism is restrained in the lock state and abbreviated "S/L," the term "normal lock" as used hereafter in the specification refers to a state that the lock/unlock mechanism is in an ordinary lock state and abbreviated "N/L," and the term "unlock lock" as used hereafter in the specification refers to a state that the lock/unlock mechanism is in an unlock state and abbreviated "U/L."
Because the super lock system, i.e. the restraint door lock system, is actuated by a power actuator, in the event that persons having an intention of committing a theft of the vehicle cuts off the electric connection between the power source battery and the electric circuit of the vehicle after breaking a window and operating a hood opener to open the hood of the engine compartment, and electrically connects these power source battery and electric circuit of the vehicle again, the power actuator recovers its operation and, however, brings the restraint door lock mechanism into release of the super lock state.
In order to be prevented from a theft, a vehicle of this type is provided with a hood opener lock means for locking a hood opener to prevent the hood of an engine compartment from being opened whenever the door lock/unlock mechanism is in the super lock state, so as thereby to deprive a person having an intention to steal the vehicle of access to the power source battery in the engine compartment. Such a hood opener lock means is known from, for example, Japanese Patent Application laid-open to the public as Publication No. No.7-26821. There has been proposed a door lock/unlock mechanism adapted to restraint release of the super lock state when re-connected to the power source battery.
While the door lock/unlock system adapted to restraint release of the super lock state when re-connected to the power source battery is desirable in light of the antitheft purpose, however, it causes a somewhat troublesome operation imposed on a driver. Specifically, in an event where, after having removed once a battery from the vehicle with the door lock/unlock mechanism of all of the door left in the super lock state, for the purpose of, for example, charging the battery or replacing the battery with a fresh one, the charged battery or a fresh battery is re-connected to the electric circuit of the vehicle with only the driver's side door having been unlocked by a door key, the remaining doors other than the driver's side door remain in the super lock state. Consequently, it is necessary for the driver to release the super lock state of the door lock/unlock mechanisms of the remaining doors before unlocking the remaining doors, which is always troublesome for the driver.